John: I probably overdo my preheat, because it's easy and I enjoy having the fire going. I have gone from cold to cooking in 2-3 hours and it was fine, but I usually do more like 3-5 hours. That's with a cold start. If I cooked the night before, the next afternoon I'm probably still at 500F-ish, maybe less if I let it cool down some before putting in the insulated door. That cuts down on preheat considerably. I'm not sure the minimum preheat because I've never rushed it. And it usually takes me an hour to build up from kindling to a real blazing fire, which could probably be shortened if I wanted to.